The manufacturing of paper has evolved over the last centuries. Modern papermaking began in the early 19th century in Europe with the development of the Fourdrinier machine, consisting in the production of a continuous roll of paper rather than individual sheets. With the aim of reducing paper making manufacturing costs, the papermaking machine has further evolved and is capable of forming at very high speeds (i.e. around 100 km/h), a large band of paper web typically measuring up to 11 meters wide. At a final step of the paper making process, the continuous paper web is wound as a roll that is used in post-processing or distribution of paper.
The papermaking process is a continuous process which cannot be readily started and stopped without incurring considerable expense. Therefore, the rolls of paper which are formed must be started and cut off from the continuously formed web without interrupting the continuous production of paper.
When the roll is fully formed, the continuous paper web is severed and redirected onto a new spool. It is common practice to use a web cutting apparatus for cutting or notching the continuous paper web so as to form a tail end and a turn-up start for assisting in the re-threading of the web from a forming roll to a new spool. As the web travels at a very high speed, the web cutting apparatus must produce a cut of the web for effectively re-threading the new spool without causing a jam in the machine and interupting production.
In PCT patent application No. PCT/US97/07615 to Beloit Technologies inc., there is disclosed a web turn-up apparatus that uses two water jets and an adhesive material dispenser such as a tape or glue dispenser. The two water jets are oriented to cut the web as it is led over a winder drum. The jets are initially positioned above the web at a center portion and each jet travels toward an opposite edge portion of the web. The two jets form a turn-up start having substantially a V-shape. The dispenser applies the adhesive material onto the turn-up start so as to provide an instant engagement of the start with the new spool, thereby assuring thereon a tight, uniform and consistent initiation of the web.
In European patent application No. EP0997417 to Voith Paper Patent GmbH, there is disclosed a method and device for severing a running web. A cutter unit is movable relative to the plane of the web and is positioned at an underside of the web. In one example, there is a cutter unit with a single cutter, the cutter is adapted to travel from one edge of the web to the opposite edge. As the web is being wound onto the forming reel, the cutter produces an oblique cut line across the web. In another example, the cutter unit has two cutters, the cutters are each adapted to travel from a center portion of the web toward opposite edges. There is presented the cut lines produced by each of the cutters as the web is being wound onto the forming reel, the cut lines cross at a middle portion and extend toward the opposite edges of the web.
In U.S. Pat. No. 6,135,000 to Paprima Industries Inc., there is disclosed a water jet cutting apparatus mounted on a beam. The beam spans across the web and is transversal to the travel direction of the web. The cutting apparatus has water jet nozzles located on opposite sides of the beam. In one example, each jet is adapted to travel along the beam from a middle portion of the beam toward an outer portion of the beam forming a pointed start on the web. Paprima further presents the cut lines formed by each water jet, as the web travels the water jets initially positioned above a middle portion form cut lines that cross and extend to opposite edges of the web. In yet another example, there is a single water jet that travels from one edge of the web to an opposite edge of the web. A skilled person would understand that with such displacement of the water jet, as the web travels there would be formed an oblique start.
As presented in FIGS. 1A and 1B, the cutting apparatus in the above mentioned references form either a pointed start 100a or an oblique cut start 100b for re-threading around a new spool and form respectively a complementary notched tail 102a or an oblique cut tail 102b for the forming spool.
The web portions (100a and 102a) of FIG. 1A, each travel at high speed in the direction indicated by the arrow, an adhesive being placed on the pointed start 100a causes this web portion to tightly engaging a new spool. However, the notched tail 102a is a loose end that has a tendency to uncontrollably flutter as it is pulled around the forming spool. The uncontrolled fluttering of the notched tail 102a can cause a rip and/or a complete detachment of a portion of the notched tail 102a thereby possibly jamming the papermaking machine, disrupting further processing operations as pieces of paper get wrapped in the forming roll and causing production loss.
In FIG. 1B, the oblique cut start 100b and tail 102b both have a shape that is possibly less prone to uncontrollably flutter as it is pulled around the forming spool. However, the complementary oblique cut start 100b may cause alignment problems when re-threading a new spool. The shape of an oblique cut start 100b is such that at re-threading, as the prominent edge of the web engages the new spool, a pulling force is initially applied only at that prominent edge. A pulling force being applied at only one edge portion does not provide a symmetric pulling force across the web, thereby possibly causing web edge alignment problems and wrinkles on the forming roll and this can be a cause for production loss.
Therefore, there is a need for a web cutting apparatus that forms a web tail portion for ending a forming spool and a web start portion for re-threading a new spool that are stable when traveling at high speed. Also there is a need for a web cutting apparatus that forms a web start portion for re-threading a new spool in a uniform edge alignment.